Spots on dogwood leaves seldom harmful
Posted on Sunday, September 7, 2008
Question: Spots and blotches appear on the leaves of my dogwood. The spots sometimes merge together and the leaves fall off the tree. I want to save my tree, is there anything I can do for it ?
Answer: Many fungi cause leaf spots on dogwood. These spots are unsightly but rarely harmful to the tree. The fungi are spread by wind and splashing water. Spots develop where the fungi enter the tissue and blotches form.
Clean up and destroy the affected leaves. If you are concerned about the health of the tree from fungus, early in the spring spray it with a fungicide such as Daconil.
Question: My redbud has sunken spots on the branches. Can I save it ?
Answer: The problem is likely canker. This widespread disease attacks wounded or stressed trees. It causes sunken cankers on the trunk and branches. If a canker encircles a branch or trunk, it kills it.
Prune branches at least 12 inches below the infection. Sterilize pruners after each cut by dipping them in alcohol. Avoid wounding healthy branches or the trunk. Keep trees healthy through proper watering and fertilizing.
Question: I planted two butterfly bushes which are doing fine. Should I cut them back this fall or wait until spring ?
Answer: Fall pruning of buddleias or any other shrub is inadvisable. Pruning inhibits the natural hardening of tissues and can increase the likelihood of winter kill. In some instances, it stimulates late growth, which is similarly tender.
It is better to wait until the worst of winter is past. Buddleia davidii, the most commonly grown species, produces flowers on the current season's growth and blooms from mid-July to frost, so you can safely cut it back to a foot or so in the spring with no loss of show. The fountain buddleia B. alternifolia flowers on last year's wood. It is easy to distinguish by the arching clusters of flowers in mid-May. Prune this species by thinning out one-third of the oldest wood after flowering.
Tip: Earthworms help decompose plant material, improve the structure of the soil and make nutrients more easily available to plants.
Send your gardening and landscaping questions and tips to Washington County Master Gardeners, 2536 N. McConnell Ave., Fayetteville, AR. You may also call 444-1755 for answers to your questions.
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